Transmission for automobiles and bearing therefor

ABSTRACT

A transmission for automobiles comprising a casing, an input shaft and an output shaft, a power transmission member on the driving side, a power transmission member on the driven side, and a bearing comprising an outer ring, an inner ring, a plurality of balls between the outer and inner rings, and seal rings provided on the opposite ends of the bearing and having an inner peripheral edge fixed to the inner ring and an outer peripheral edge to form a small gap for a labyrinth seal between the outer peripheral edge and the outer ring whereby particle matter can go out of the bearing through the small gap during rotation of the bearing.

FIELD OF THE INVENTION

The present invention is related to a transmission for automobiles and abearing for use in the transmission.

BACKGROUND OF THE INVENTION

Generally, a rolling bearing fitted with a seal ring (referred tohereunder as a seal ring fitted rolling bearing) is incorporated for useinto a transmission for automobiles, and onto a rotational supportsection of various types of machinery such as machine tools andelectrical machines.

The transmission for automobiles of the present invention is providedbetween an engine and a driven wheel, and is used for changing the ratiobetween the rotational speed of the engine crank shaft and therotational speed of the driven wheel. Here the transmission forautomobiles, which is the object of the present invention, includes aswell as manual transmission, automatic transmission of variousconstructions such as planetary gear systems, belt systems, and toroidalsystems.

As a transmission for automobiles incorporating a seal ring fittedrolling bearing, there is disclosed in U.S. Pat. No. 4,309,916 aconstruction as shown in FIG. 5. This manual type transmission forautomobiles shown in outline in FIG. 5 has lubricating oil (transmissionoil) 30 contained inside a casing 29, and an input shaft 31 and anoutput shaft 32 provided concentrically and freely rotatable relative toeach other inside the casing 29. Furthermore, a transmission shaft 33 isprovided inside the casing 29, parallel with the input shaft 31 and theoutput shaft 32. The input shaft 31, output shaft 32 and transmissionshaft 33 are each rotatably supported by ball bearings 1 a with sealrings fitted therein (referred to hereunder as seal ring fitted ballbearings) for serving as rolling bearings.

Of these shafts, the input shaft 31 supports a driving side gear 34serving as a power transmission member on the driving side. Moreover,the input shaft 32 supports by means of respective synchromesh units(not shown in the figure), driven side gears 35 a, 35 b, 35 c and 35 dserving as respective power transmission members on the driven side. Atthe time of operation, only one of the driven side gears 35 a˜ 35 drotates with the output shaft 32, the other driven side gears rotatingrelative to the output shaft 32. Furthermore, the transmission shaft 33,on the part facing the driving side gear 34 and the respective drivenside gears 35 a, 35 b, 35 c and 35 d supports respective transmissiongears 36 a, 36 b, 36 c, 36 d and 35 e so as to be rotatable togetherwith the transmission shaft 33. The respective transmission gears 36 a,36 b, 36 c, 36 d and 36 e are respectively engaged with the driving sidegear 34 and the driven side gears 35 a, 35 b, 35 c and 35 d eitherdirectly or via an idler gear 37 used for reversing.

In the case of the invention disclosed in the abovementioned U.S. Pat.No. 4,309,916, the respective seal ring fitted ball bearings 1 aincorporated into the transmission for automobiles such as describedabove are sealed type bearings filled with grease. This is to say, forthese respective seal ring fitted ball bearings 1 a, ones constructed asshown in FIG. 6 are used. This seal ring fitted ball bearing 1 acomprises an outer ring 2 and an inner ring 3 disposed concentric witheach other, a plurality of balls 4 serving as rolling members, aretainer 5, and a pair of seal rings 6 a. An outer ring raceway 7provided on a central portion of the inner peripheral face of the outerring 2, and an inner ring raceway 8 is provided on the central portionof the outer peripheral face of the inner ring 3. The balls 4 areprovided between the outer ring raceway 7 and the inner ring raceway 8and are retained by the retainer 5 so as to be freely rotatable. Due tothe rotation of the plurality of balls 4, the outer ring 2 and the innerring 3 are freely rotatable relative to each other.

Moreover, anchoring grooves 9 are formed on opposite end portions on theinner periphery of the outer ring 2 around the whole periphery. A pairof ring shaped seal rings 6 a are provided the outer peripheral rimportions of which are anchored in the respective anchoring grooves 9.The seal rings 6 a are formed in an overall ring shape from respectivering shaped metal rings 14 and resilient material 15 such as rubber likeelastomer etc.. The resilient material 15 has seal lips 13 the tip edgerims of which are provided on the inner peripheral rims of the resilientmaterial 15 to go into respective recesses 12 formed around the wholeperiphery of the outer peripheral face portions on the opposite ends ofthe inner ring 3, and come into sliding contact with a portion of theserecesses 12.

In the case of the seal ring fitted ball bearing 1 a constructed asdescribed above, communication between a space 16 in which the balls 4are disposed and the outer space outside of the space 16 is shut off.Hence foreign matter existing outside cannot enter into the space 16.Therefore, any increase in wear due to foreign matter at the contactportions between the outer ring raceway 7 and the inner ring raceway 8and the rolling surfaces of the balls 4 is prevented, thus enabling anincrease in the rolling fatigue life of the seal ring fitted ballbearing 1 a.

With the rolling bearing incorporated into a transmission forautomobiles as described above for rotatably supporting the shafts 31,32 and 33 prior to the invention disclosed in U.S. Pat. No. 4,309,916, aso called open type ball bearing 38 having no seal rings as shown inFIG. 7, was used. Lubrication of this ball bearing 38 is affected bycirculation of lubricating oil 30 (FIG. 5) contained inside the casing29. However, hard foreign matter such as wear debris and shavings fromthe respective gears 35 a, 35 b, 35 c and 35 d, 36 a, 36 b, 36 c, 36 dand 36 e mixed into the lubricating oil 30, and this foreign matterdamages the outer ring raceway 7, the inner raceway 8, and the rollingsurfaces of the balls 4 giving an increase in wear, so that theendurance of the ball bearing 38 is compromised. On the other hand, inthe case of the above described seal ring fitted ball bearing 1 a shownin FIG. 6, this foreign matter does not damage the outer ring raceway 7,the inner ring raceway 8 and the rolling surfaces of the balls 4, andhence the rolling fatigue life can be increased.

In the case of the seal ring fitted ball bearing 1 a shown in FIG. 6,the seal rings 6 a made up of the metal ring 14 and the resilientmaterial 15 are used. Furthermore, lubricating grease is filled in theinterior and hence cost increased. Specifically, since the seal rings 6a are a tight seal having substantially no gap, it takes a substantiallylong time before the lubricating oil existing around the seal ringfitted ball bearing 1 a enter the interior of the of the seal ringfitted ball bearing 1 a for lubrication. Accordingly, the grease must befilled in it. In addition, when the lubricating oil 30 inside the casing29 of the transmission for automobiles is exchanged, this grease remainsunchanged. Consequently, lubrication of the seal ring fitted ballbearing 1 a must be effected by the initially introduced grease, eventhough the lubricating oil 30 is exchanged several times. It istherefore necessary to use an expensive grease having a very long life,thus causing an increase in the overall cost of the seal ring fittedball bearing 1 a. Moreover, in the case of the seal ring fitted ballbearing 1 a, since the seal lips 13 rub against the recesses 12,rotational torque is increased.

In view of the above situation, the present inventors have consideredusing a construction such as shown in FIG. 8 as a seal ring fitted ballbearing incorporated into the rotational support sections of variousmechanical equipment such as transmissions for automobiles. In the caseof the seal ring fitted ball bearing 1 shown in FIG. 8, a pair of ringshaped seal rings 6 are provided the outer peripheral rims of which areanchored in the anchoring grooves 9 formed in inner peripheral faceportions on the opposite ends the outer ring 2 around the wholeperiphery thereof. That is to say, bent back portions 10 on the outerdiameter side are formed on the outer peripheral rim portions of thethin metal plate seal rings 6, by bending back the outer peripheral rimportions of the thin metal plate to give an arcuate shape incross-section, and the bent back portions 10 on the outer diameter sideare tightly crimped into the anchoring grooves 9 so that the seal rings6 are securely supported on the outer ring 2.

Moreover, bent portions 11 are formed on the inner peripheral rims ofthe seal rings 6, and the inner peripheral faces of these bent portions11 faces recesses 12 formed in the outer peripheral faces of theopposite end portions of the inner rings 3 around the whole peripherythereof. These recesses 12 and bent portions 11 of the seal rings 6constitute labyrinth seals, and prevent the ingress of external foreignmatter into the space 16 between the inner peripheral face of the outerring 2 and the outer peripheral face of the inner ring 3, in which theballs are disposed.

In the case where a seal ring fitted ball bearing 1 constructed asdescribed above is used for example for supporting the shafts 31, 32 and33 constituting a transmission for automobiles such as shown in FIG. 5,the lubricating oil 30 contained inside the casing 29 is calculatedinside the space 16 in which the balls 4 are disposed to therebylubricate the contact portions of the outer ring raceway 7, the innerring raceway 8 and the rolling faces of the balls.

The present inventors used the seal ring fitted ball bearing 1 as shownin FIG. 8 for supporting the various shafts 31, 32 and 33 constituting atransmission for automobiles such as shown in FIG. 5, and carried outexperiments to determine the endurance. Instead of being better than forthe case where the open type ball bearing 38 such as shown in FIG. 7 wasused, the endurance was worse. While researching the reason for this,the present inventors identified the following cause. That is to say, inthe case of the seal ring fitted ball bearing 1 shown in FIG. 8, theingress of foreign matter to inside the space 16 can not be completelyprevented by the labyrinth seal made up of the recesses 12 and the bentportions 11 of the seal rings 6. Furthermore, the foreign matterentering into the space 16, accumulated at the outer diameter side ofthe space 16 due to centrifugal force, and was blocked by the seal rings6 from being discharged from inside the space 16, thus remainingthereinside. As a result, wear due to the foreign matter was increasedat the contact portions of the outer raceway 7 and the inner ringraceway 8, and the rolling faces of the balls 4, thus shortening therolling fatigue life of the seal ring fitted ball bearing 1.

On the other hand, in Japanese Patent Publication TOKUKAIHEI No.8-114235, and Japanese Utility Model Publication JITSUKAISHO Nos.51-79252,54-95655, 58-86925, 60-7326, and 60-89422, a seal ring fittedball bearing is disclosed where the inner peripheral rims of seal ringsare anchored in the outer peripheral surfaces on the end portions of aninner ring, and a labyrinth seal is provided between the outerperipheral rims of the seal rings and the inner peripheral surfaces ofthe end portions of an outer ring. However, with the seal ring fittedball bearings disclosed in these publications, no consideration is givento lubrication using lubricating oil which is contaminated with hardforeign matter such as the wear debris and shavings from gears, such aswith the transmission for automobiles.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a transmission forautomobiles and a bearing for use in the transmission, taking the abovesituation into consideration, which can be provided at a low cost withlong life and minimal rotation torque, and with minimal drive powertransmission loss and excellent endurance, even in the case wherelubrication is carried out using the lubricating oil where there is thepossibility of hard foreign matter contamination.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional partial view of an example of theembodiments of the seal ring fitted rolling bearing of the presentinvention.

FIG. 2 is a cross sectional partial view of another example of theembodiments of the seal ring fitted rolling bearing of the presentinvention.

FIG. 3 is a cross sectional partial view of another example of theembodiments of the seal ring fitted rolling bearing of the presentinvention.

FIG. 4 is a graph to show a result of the experiments conducted toconfirm the effects of the present invention.

FIG. 5 is a diagrammatic cross sectional view of an example of theembodiments of the transmission for the automobiles in which a seal ringfitted rolling bearing in the prior art is incorporated.

FIG. 6 is a cross sectional view of an example of the embodiments of theseal ring fitted rolling bearing incorporated into the transmission forautomobiles of FIG. 5.

FIG. 7 is a cross sectional view of an example of the embodiments of theball bearing of the open type.

FIG. 8 is a cross sectional view of an example of the embodiments of theseal ring fitted rolling bearing having a small gap on the side of theinner peripheral edge.

PREFERRED EMBODIMENTS OF THE INVENTION

According to the one embodiment of the present invention, the seal ringfitted rolling bearing comprises an outer ring having an innerperipheral face formed with an outer ring raceway, an inner ring havingan outer peripheral face formed with an inner ring raceway, a pluralityof rolling members provided between the outer ring raceway and the innerring raceway, and a pair of seal rings formed generally in a circularshape to cover the openings on the opposite ends of the space betweenthe inner peripheral face of the outer ring and the outer peripheralface of the inner ring where the rolling members are provided, which issimilar to the prior art seal ring fitted rolling bearings.

In the seal ring fitted rolling bearing of the embodiment, the contactportions between the outer ring raceway, inner ring raceway and rollingfaces of the rolling members are lubricated by supply of the lubricateoil in the space which hard foreign matter may enter from outside duringuse.

At least one of the seal rings has an inner peripheral edge which isanchored and fixed in a portion of the outer peripheral face of theinner ring at the end thereof away from the inner ring raceway, and itsouter peripheral edge is located close to the end edge faces of theouter ring, so that there is a small gap between the outer peripheraledge of the aforementioned seal ring and the end edge face of the outerring which allow the hard foreign matter mixed in the lubricant oil passtherethrough. Further, with centrifugal force produced during use, thelubricant oil supplied in the space can be discharged outside the spacethrough the small gap together with the hard foreign matter mixed in thelubricant oil. This reduces the amount of foreign matter mixed in thelubricant oil for lubrication of the contact portions between the outerring raceway, inner ring raceway and the rolling faces of the rollingmembers, preventing the reduction in rolling fatigue life due to theforeign matter.

Further, according to another embodiment of the present invention, atransmission for automobiles comprises a casing in which lubricant oilis reserved, input and output shafts each rotatably supported by abearing(s) in the casing, respectively, a power transmission member onthe driving side supported by the input shaft to rotate with the inputshaft, and a power transmission member driven side supported by theoutput shaft to be engaged with the power transmission member on thedriving side for power transmission, and to rotate with the output shaftas the input shaft rotates, which is similar to the conventionaltransmission for automobiles.

In this embodiment, the transmission for automobiles uses the seal ringfitted rolling bearing of the embodiment mentioned above. Thereof, theendurance of the transmission for automobiles is improved.

Now, FIG. 1 shows a first example of an embodiment of the presentinvention. One feature of the present invention is the point that theinner peripheral rim portions of a pair of seal rings 19 are anchoredand secured to the outer peripheral faces on opposite ends of an innerring 3.

Another feature of the present invention is the point that, due to theconstruction as mentioned above, small gaps 24 are formed between theouter peripheral rim portions of the seal rings 19 and the innerperipheral faces 25 on the end portions of an outer ring 2, so thatduring use, it is difficult for foreign matter to enter into a space 16and that any foreign matter that has entered is discharged to outside ofthe space 16 from the small gaps 24 together with lubricating oilsupplied to the space 16, due to the centrifugal force added during use.

Other details of the construction and operation are the same as for theconventional construction shown in FIG. 6 and FIG. 8, and hence similarcomponents are denoted by the same symbols and repeated description isomitted or abbreviated. Hereunder the description is centered on thecharacteristic parts of the present invention.

Anchoring grooves 20 are formed in the outer peripheral face of theinner ring 3 at opposite end portions away from the inner ring raceway8, around the whole periphery. Furthermore, there is a pair of sealrings 19, each made from a thin metal plate and ring shaped, the innerperipheral rims of which are anchored and secured to the respectiveanchoring grooves 20.

That is to say, a bent back portion 21 on the inner diameter side isformed on the inner peripheral rim portion of each of the seal rings 19,by bending back the inner peripheral rim portion of thin metal plate togive an arcuate shape in cross-section. Moreover, the bent back portions21 on the inner diameter side are tightly crimped onto the anchoringgrooves 20, so that the seal rings 19 are securely supported on theouter peripheral faces of the opposite end portions of the inner ring 3.

Furthermore, a bent portion 22 is formed on the outer peripheral rim ofeach of the seal rings 19. The outer peripheral faces of these bentportions 22 are made close to the end edge faces, that is the innerperipheral faces 25 of the opposite end portions of the outer ring 2around the whole periphery.

Moreover, formed between the outer peripheral rim portions of the sealrings 19 and the inner peripheral faces 25 of the opposite end portionsof the outer ring 2 around the whole periphery are small gaps 24 whichfreely allow the passage of foreign matter mixed in the lubricating oil.

Furthermore, recesses 23 are formed around the whole periphery in theinner peripheral face of the outer ring 2 at the portions on the axiallyinner side than the inner peripheral faces 25 of the end portions (onthe axial center side of the seal ring fitted ball bearing 18).

The outer peripheral faces of the bent portions 22 are made to facethese recesses 23, thus making up a labyrinth seal. Hence the entry offoreign matter existing outside into the space 16 which the respectiveballs 4 are disposed between the inner peripheral face of the outer ring2 and the outer peripheral face of the inner ring 3 is prevented (keptto a minimum).

In the case where the seal ring fitted ball bearing 18 of the presentexample constructed as described above is incorporated into for examplea transmission for automobiles such as shown in FIG. 5, the inner rings3 are externally secured to the respective shafts 31, 32 and 33, theouter rings 2 are internally fixed to support bores 40 formed in partssuch as support walls 39 secured to the casing 29.

At the time of operating the transmission for automobiles, thelubricating oil 30 contained inside the casing 29 is agitated by therespective gears or is supplied to close to the seal ring fitted ballbearings 18 by means of an oil supply pump (not shown in the figure),and passes through the respective small gaps 24 into the space 16,thereby lubricating the contact portions of the outer ring races 7, theinner ring races 8 and the rolling faces of the balls 4.

During operation the transmission for automobiles, when the inner ring 3rotates with rotation of the respective shafts 31, 32 and 33, the sealrings 19 securely anchored with the outer peripheral face portions onthe ends of the inner ring 3, rotates together with the balls 4. Withthe rotation of the inner rings 3, the seal rings 19 and the balls 4,the lubricating oil existing inside the space 16 also rotates, so that acentrifugal force is imparted to the lubricating oil. As a result, thelubricating oil moves to the outer diameter side of the space 16 (towardthe inner peripheral face side of the outer ring 2), and is thendischarged from respective small gaps 24 to outside of the space 16. Atthis time, foreign matter mixed in the lubricating oil is dischargedtogether with the lubricating oil to outside of the space 16.

In particular, wear debris and shavings with a higher specific gravitythan the lubricating oil are effectively discharged, passing through thesmall gaps 24 to outside of the space 16.

Moreover, during operation of the transmission for automobiles,lubricating oil is continuously supplied to inside the space 16, andhence lubrication of the contact portions of the outer ring raceway 7and the inner ring raceway 8 and the rolling faces of the balls 4 issuitably carried out. That is to say, during operation of thetransmission for automobiles, lubricating oil is continuously suppliedto inside the space 16, and is successively discharged.

While it is possible for a small quantity of wear debris and shavings tobe mixed with the lubricating oil supplied to inside of the space 16,since wear debris and shavings of high specific gravity are effectivelydischarged, there is a tendency for only lubricating oil which is notmixed with such wear debris and shavings remain inside the space 16, andhence damage to the outer ring raceways 7 and the inner ring raceways 8and the rolling surfaces of the respective balls 4 is minimized.

When using the seal ring fitted ball bearing 18, then also in the casewhere the outer ring 2 rotates, based on the revolving movement of theballs 4, a centrifugal force is imparted to the lubricating oil.Consequently, as with the case where the inner ring 3 rotates, thelubricating oil contaminated with foreign matter is discharged from thesmall gaps 24 to outside of the space 16.

The supply of lubricating oil to inside the space 16, as well as beingcarried out via the small gaps 24 as mentioned above, can also involvesupply from the inner peripheral rim side of the seal rings 19. That isto say, a splash method where lubricating oil splashed towards the innerperipheral rim portions of the seal rings 19 from external spaceexisting outside of the space 16, or an oil bath method where the sealring fitted ball bearing 18 is used part thereof immersed in thelubricating oil 30 (FIG. 5) contained inside the casing 29 (thecondition where the lubricating oil reaches as far as a part of theinner peripheral rim portions of the seal rings 19) is adopted.

For example in the case of the present example, the supply of thelubricating oil to inside the space 16 can be carried out through a gapbetween the bent back portions 21 on the inner diameter side formed onthe inner peripheral rim portions of the seal rings 19, and therespective anchoring grooves 20. That is to say, a small oil supply gapthrough which only lubricating oil can pass and foreign matter cannotpass is provided in the engaging portions between the bent back portions21 and the respective anchoring grooves 20, so that lubricating oil canfreely flow to inside the space 16 via this oil supply gap.

Here such a small oil supply gap is formed for example by smallundulations provided on at least one face of the mutually opposing facesof the bent back portions 21 on the inner diameter side and theanchoring grooves 20.

FIG. 2 shows a second example of an embodiment of the present invention.With this example, the point that differs from the abovementioned firstexample is that a small gap 24 a is formed in a conical cylinder shape.

Therefore, with this example, the bent back portions 22 a with theirdiameters increasing towards the respective widthwise end portions ofthe seal ring fitted ball bearing 18 a, are formed on the respectiveouter peripheral rims of the pair of the seal rings 19 a. Moreover, theinner peripheral faces 25 a on the opposite ends of the outer ring 2 areformed in a conical concave shape, and the respective outer peripheralfaces of the bent back portions 22 a faces close to the inner peripheralfaces 25 a, around the whole periphery.

The small gaps 24 a through which foreign matter mixed in thelubricating oil can pass freely, are formed around the whole peripherybetween the outer peripheral rim portions of the seal rings 19 a and theinner peripheral faces 25 a of the end portions.

The diameter of these small gaps 24 a which make up labyrinth seals,increases with distance from the space 16, so that the lubricating oilsupplied to inside the space 16, is effectively discharged freelytogether with foreign matter contained therein to away from the space16, due to centrifugal force.

Step portions 26 are formed in the outer peripheral face of an innerring 3 at opposite end portions away from the inner ring raceway 8,around the whole periphery.

Furthermore, the inner peripheral rims of the seal ring 19 a, each ringshaped, are externally secured to the respective step portions 26. Thatis to say, the bent back portions 27 on the inner diameter side areformed by bending back the inner peripheral rim portions of the sealring 19 a made from a thin metal plate give an L-shape in cross-section.The bent back portions 27 on the inner diameter side are externallyfitted to the step portions 26 so that the seal rings 19 a are securelysupported on the inner ring 3.

Furthermore, through holes 28 are provided at a plurality of locationsaround the periphery of the bent back portions 27 on the inner diameterside serving as passages for communicating between the space 16 and theexternal space existing around the seal ring fitted ball bearing 18 a.The shape of the through holes 28 is optional being for example circularof slit shape.

In case of the seal ring fitted ball bearing 18 a of this exampleconstructed as described above, the small gaps 24 a are formed in aconical cylinder shapes with their diameters increasing towards theopposite end portions of the seal ring fitted ball bearing 18 a.Therefore, in the case of this example, the lubricating oil entering thesmall gaps 24 a is effectively discharged towards the external space.That is to say, due to the centrifugal force acting on the lubricatingoil existing inside the small gaps 24 a, a diametrically outwarddirected force (in the upward direction in FIG. 2) is applied to thelubricating oil. Due to this force, discharge of the lubricating oil canbe effectively carried out.

Moreover, supply of lubricating oil to inside the space 16 is carriedout from the through holes 28.

Other details of the construction and operation are the same as for thecase of the above described first example including the case where thisis fitted to the rotation support sections of a transmission forautomobiles, and hence similar components are denoted by the samesymbols, and repeated description is omitted.

FIG. 3 shows a third example of an embodiment of the present invention.In the case of the seal ring fitted ball bearing 18 b of this example,resilient material 15 a such as rubber or synthetic resin or the like isbonded to the outer peripheral rim portions of the pair of seal rings 19b around the whole periphery. That is to say, the seal rings 19 b aremade up of metal rings 14 a and the resilient material 15 a. Moreover,the outer peripheral faces of the resilient material 15 a are positionedclose to the inner peripheral faces 25 a on the end portions of theouter ring 2 around the whole periphery.

Furthermore, the small gaps 24 b through which foreign matter mixed inthe lubricating oil can pass freely are formed between the outerperipheral rims of the seal rings 19 b and the inner peripheral faces 25a of the end portions of the outer ring 2, around the whole periphery.

The resilient material 15 a is finished with accurate dimensions (outerdiameter) by mould forming to the outer peripheral rim of the metalrings 14 a. Furthermore, even though part of the resilient material 15 amay rub against part of the outer ring 2, there is practically no lossof function of the seal ring fitted ball bearing 18 b. Consequently inthe case of this example, the width of the small gaps 24 b is madesmaller than the width of the small gaps 24 a of the abovementionedsecond example, so that the ingress of foreign matter through the smallgaps 24 b to inside the space 16 can be more effectively prevented.

In the case of the seal ring fitted ball bearing 18 b of the exampleconstructed as described above, since the small gaps 24 b can be madesmall, the sealing by the seal rings 19 b can be improved.

Other details of the construction and operation are the same as for thecase of the above described second example including the case where thisis fitted to the rotation support sections of a transmission forautomobiles, and hence similar components are denoted by the samesymbols, and repeated description is omitted.

WORKING EXAMPLES

Next is a description of experiments carried out by the present inventorto confirm the effects of the present invention. These experiments usedthe seal ring fitted ball bearing 18 of the first example of theembodiments of the present invention shown in FIG. 1. Moreover as acomparative example, two types were used, namely the heretoforegenerally used open type ball bearing 38 (comparative example 1) whichdid not have a seal ring, as shown in FIG. 7, and the seal ring fittedball bearing 1 (comparative example 2) having small gaps on the innerperipheral rim side as shown in FIG. 8.

With these experiments, the respective specimens were fitted to a testrig and the inner 3 ring rotated while lubricating the containingportions of the outer ring raceway 7 and the inner ring raceway 8 andthe rolling surfaces of the balls 4. The rolling fatigue life of therespective test pieces was then observed.

The data of the ball bearings used in the respective tests, and the testconditions related to these are as follows.

1. Data for the ball bearings used: deep groove ball bearings withdesignation number 6206 (outer diameter 62 mm, inner diameter 30 mm, andwidth 16 mm)

2. Test conditions. Lubrication condition: test rig was run under thefollowing conditions with the shaft secured inside the inner ring of therespective test pieces immersed in ATF (automatic transmission fluid)lubricating oil up to the axial center of the shaft.

Rotational speed: 6000 rpm

Radial load: 612 kgf.

Oil temperature: 125° C.

Foreign matter as described below was introduced to the ATF as follows;Weight of the foreign matter (particles) in the lubricating oil (ATF):10-30 micron diameter particles, and 75-150 micron diameter particles,each at 100 ppm.

Under the above conditions, the rolling fatigue life of the respectivetest pieces was obtained giving the results as shown in FIG. 4. In FIG.4, (Δ) is Example 1, (∘) is Comparative Example 1 and (□) is ComparativeExample 2. The horizontal axis shows the rolling fatigue life (time) ofthe respective test pieces, while the vertical axis shows the cumulativedamage probability (%) of the respective test pieces.

The rolling fatigue life of the respective test pieces for when thedamage condition was the same (when the cumulative damage probabilitywas 10%) is shown respectively in Table 1.

As is clear from FIG. 4 and Table 1, the rolling fatigue life of theseal ring fitted ball bearing of the present invention was longer thanthe rolling fatigue life of the Comparative Examples 1 and 2. Morespecifically, with Example 1 according to the present invention, it wasverified that a rolling fatigue life of more than 4.5 times that forComparative Example 1, was obtained.

TABLE I Rolling fatigue life₁₀ (time) Life ratio Comparative Example 132.32 1 Comparative Example 2 25.09 0.80 Example 1 144.73 4.62

The present invention, due to the above described construction andoperation realizes a seal ring fitted ball bearing having low torque andlong life at a low cost. Furthermore, the invention realizes a low costtransmission for automobiles having minimal power loss and excellentdurability.

What is claimed is:
 1. A transmission for automobiles comprising: acasing, an input shaft and an output shaft, a power transmission memberon a driving side of the transmission, a power transmission member on adriven side of the transmission, and a bearing comprising an outer ring,an inner ring, a plurality of balls, and a plurality of seal rings eachhaving an inner peripheral edge fixed on the inner ring and an outerperipheral edge, each outer peripheral edge being spaced from the outerring such that a small gap is formed between each outer peripheral edgeand the outer ring.